homelab: v0.6.0 — usage telemetry (usage top), evidence-driven verb prioritization

Answers the question that drove the whole CLI — which verbs to add next — with
data instead of one maintainer's habits, and resolves the cross-user-usage ask
in-bounds (no reading anyone's home).

- emit on dispatch: every verb fire-and-forgets one Loki line {job,user,verb} +
  "exit=N ver=X". ONLY the verb path + exit code — never args, paths, flags, or
  secrets (the emit never sees arguments). Best-effort: 800ms timeout, errors
  swallowed, never affects the command; opt-out HOMELAB_TELEMETRY=0. Discovery
  verbs (manifest/version/help) and usage itself don't self-record.
- usage top [--since 30d] [--user U] [--json]: ranks verbs via
  sum by (verb)(count_over_time({job="homelab-usage"}[…])) against the shared
  Loki. Cross-user analytics WITHOUT touching ~/.claude — the privacy-preserving
  answer to "what does the team use".
- Loki sink (zero new infra, dogfoods v0.5 logs path); push verified HTTP 204 no
  auth. ADR docs/adr/0011.

Live-verified: ran 4 verbs, usage top ranked them correctly (metrics query=2).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

cli/homelab.go

@@ -20,6 +20,7 @@ func buildRegistry() []Command {
 	reg = append(reg, deployCommands()...)
 	reg = append(reg, netCommands()...)
 	reg = append(reg, obsCommands()...)
+	reg = append(reg, usageCommands()...)
 	return reg
 }